Ionic bombardment light source



IONIC BOMBARDMENT LGHT SOURCE Filed Dec, 4, 1950111111111111111;rllflllllllllllzrll @miden/5f RAYMOND T. CLOUD,

Patented Feb. 21, 1933 UNITED STATES `PATENT OFFICE 0F CHICAGO,ILLINOIS, ASSIGNOB,

BY IIBNE ASSIGNMENTS, T0

or New Yoax, N. Y., .a coaroaa'rron or rome nonanbunn'r Liam' sonnenApplication llled December 4, 1930. Serial No. 489,898.

GENERAL THEATERS EQUIPMENT, INC., DELAWARE These improvements relate tolight sources of the kind in which an incandescent surface is producedby ionic bombardment.

y copending4 application Ser. No. 423,600, filed January 27, 1930, haveillustrated and described several diierent embodiments of lamps or tubesoperating on the same principle as the one herein disclosed and have inthat specification described fully the principles and operationsinvolved in such a device.

1n my copending application filed concurrently herewith as Ser. No.499,897, Ihave described and claimed certain compositions of matteruseful with the present and said embodiments of the tube.

This application is directed chiefly to a lamp construction in whichthere is a thir electrode useful under some conditions for starting theoperation. It presents also some other constructional variations fromsai first-mentioned copending application.

The prime object of the invention is to rovide a light source of highintrinsic rightness useful in recording or re reducing sound, intelevision, etc. Nota le features of this tube are uniformity in actionand its possibilit of providing substantially a oint source o light ofhigh actinic value. @ther objects and advantages will appearhereinafter.

lin the drawin gitudinal section tube;

Fi 2 is an enlarged fragmentary section showing arts of Fig. 1;

Fi 3 is a greatly enlarged vertical longitu inal section through thecathode proper and its carrier shell, with a fragment of a forming toolassociated therewith and also in longitudinal section;

Fi 4 shows the cathode elements as in Fig. 3 with the addition of afragment of the surrounding sleeve; and

Fig. 5 shows conventionally the output of an amplifying circuit havingassociate therewith a starting circuit lamp.

The device of Fig. 1 includes a base 10 in which is set the elongatedglass tube 11 Figure 1 is a vertical lonthrough my improved d with theend of for the present` turned inward atthe base portion to Vform thestem 12 flattened at 13. A conductor 14 is connected to terminal 15 inthe base, another conductr 16 is connected to base terminal 17, while athird conductor 18 is connected to base terminal 19. The constructionthus described is according to common practice in the tube art.

Conductor 14 is connected to a conductor 20 which may approximately be atun sten wire and which terminates in an expose end or. electrode at 21.A sleeve 22 of highly refractory material, such as ma esia, iits uponconductor 20. This electro e 21 is for startin the action of the lamp.55

Con uctor 16 has connected to it a conductor 23 (the cathode member)which terminates in the end portion marked 24 and which is about evenwith electrode 21. A sleeve 25 of the refractory material, as magnesia,is placed upon this cathode conductor To conductor 18 is secured aconductor 26 which should be of tungsten or other metal that seals withthe type to which in turn is secured a metallic band.- like ring 27,suitably of nickel, and which encompasses the electrodes 21 and 24 withthe electrode 24 in the center of the vring formation. This ring 27 isthe anode.

Turning to Fig. 3 it will be observed that the front end portion 24 ofcathode conductor 23 has a hollow interior filled with material 30. Thewire 23, or at least the front end portion 24, is of some metal having ahigh melting or fusing point such as tungsten or tantalum. I prefertantalum for this rod or wire 23 or for the part 24 as-that metal iseasier to work than tungsten, and its fusing point is very high.

In the originally-squared-oi end of rod 23, I bore the cylindricalrecess 31 and fill same with the material of my said secondlymentionedcopending application, packing the same therein tightly and almost flushthe rod. That is to say, I pack i'n the material until the hole orrecess 31 is almost filled. Then by means of a of glass used, and '75rotating toolas 33 (Fig. 3) having a conical 4 recess 34, I swage orburnish over the side walls 24a of the electrode holder or part 24. Thishas the effect of further compressing the material 30 in the recess, offorming retaining means for it, and further, of reducthe size of theopening as 29 through lwnich the material 30 is exposed. I recommend asize of opening 29 ranging from six thousandths of an inch to tenthousandths of an inch in diameter.

The material 30 is thercathode proper. It has high electron-emissiveproperties and high heatresisting properties. In its preferred form itconsists of thorium oxide (ThO,), 80% by weight, giving the mixture highheat-resisting qualities, and barium oxide (BaO), 20% by wei ht, whichis the highly-emissive element. hese substances are mixed thoroughlytogether and maintained free of moisture as by carrying in a dessicatoruntil the time of use. A

he barium oxide is first preliminarily heated to about seventeen hundreddegrees Fahrenheit where ebullition takes place, the heating beingcontinued until the mass becomes quiescent in the Crucible. It is thenround to a line powder and mixed with t e powdered thorium oxide.

' The ring 27 is the anode. In my practice it glows at its outer marginwith a typical purplish corona glow. The exposed surface at 36, however,is intensely bright and incandescent due to ionic bombardment. Thecorona low at the margin of anode 27 is not use by me. It may beshielded off in various ways, as by a black coating 38 applied upon theoutside of the end portion of tube 1l leaving a clear axial area at 39through which the light from the cathode surface at 36 projects.

It is pointed out in this connection that the area of the material 30 exosed as at 36 may be only a few thousandt s of an inch in diameter toproduce a highlyk eilicient light source for recording sound. I employan exposed area of the material of about ten thousandths of an inch indiameter and thereb obtain substantially a point source of lig t. Thearea of exposure may be varied within considerable limits, according tothe amount of light desired for a particular purpose.

It is fairly diilicult to com act the cathode material in a recess onlya liew thousandths of an inch in diameter. Accordingly the cylindricalrecess 3l is made more in. the nature of from twenty thousandths totwenty-iive thousandths of an inch in diameter or as may be preferred.The spinning over of the free end of the electrode reduces the openin 29as may be desired, say to a diameter o? ten thousandths of an inch.

Using referably as low a potential as possible ihr the proper operationof the lamp the tube will ordinarily require a current flow of greaterpotential to get it startlamp current conductors provided the starterprimary 41 has a secondary 42 one end of which is connected throughconductor 43 to the anode 27. The other end of secondary 2 is connectedthrough conductor 44 to cathode 24. This arrangement rovides a circuitfor exciting the lamp duri'ng the normal operations whereby theintrinsic brightness of the cathode proper varies in proportion to thevariations of current in the output of the ampliiier tube 40. Currentfor the lamp is sup lied by battery 46 which with resistance 47) isbrldged across the condenser 48. Resistance 47 may be variously from sayonethousand ohms to ten thousand ohms and is adapted to re ulate theexciting current for the tube. T e resistance 50 will be from say twohundred ohms to four hundred ohms and is preferably greater than thenegative resistance of tube l1.

The starting circuit is bridged between the 43 and 44, starting withconductors 51 andv 52. Resistance 53 may be of the order of about tenthousand ohms. Conductor 54 leading from resistance 53 leads to aContact 55 which is shown contacting switch leaf 56 from which conductor57 leads to plate 58 of condenser 59. The effect therefore is to chargeplate 58 from line 43.

Conductor 52 leads to contact 60 shown as being in contact with switchleaf 6l connected by wire 62 to plate 63 of condenser 59, thus chargingplate 63 from line 44.

his arrangement provides that when plug 65 is in the open position, asshown, the current bridged across the lamp-exciting circuit is chargingthe plates of condenser 59. Now when plug 65 is moved forward leaf 56makes contact with contact 66 connected by wire 66a to wire 52, and leafl'makes contact with contact 67, the latter being connected by a wire 68to a resistance 69 of about two thousand through wire 70 to electrode2l.

It will thus be seen that when the plug 65 is moved to spread the leaves56 and 61 condenser plate 63 is connected to electrode 2l whilecondenser plate 58 is connected to cathode 24. Under these conditions adischarge takes place between starting electrode 21 and cathode 24. Theensuing ionization instantly starts the o eration of the tube. When theoperator esires to start he merely touches a switch button repreohms,and thence 'filled with an inert gas such sented by plu 65 to dischargecondenser 59.

Resistance g2 (of about twenty thousand ohms) and resistance 7 3 (ofabout ten thousand ohms) connecting lines 43 and 44 respectively withWire maintains the starting electrode 21 at positive potentialwherenegative swings of the signalcarrying current, should the lamp goout the operation Will automatically re-start. After the lamp isinitially started and gets heated it will thus automatically re-startwhen temporarily put out. lt is only when the lamp is cold that the`starting feature is used.

rihe tube 11 is to bey considered as being as nitrogen, argon, helium,etc., at some low pressure. in my practice Withl the particular form oflamp illustrated herein I employ nitrogen gas at a pressure of aboutforty millimeters of mercury.

l claim:

l. in an ionic bombardment incandescent light source device of thecharacter described, the combination of an electrode comprising a holderfor a cathode proper, said holder having a recess therein, a cathodeproper comprising a material of substantially high ion-emissiveproperties and high heat-resisting properties and being in finelydivided forni tightly packed in said recess, and an anode electrode,said electrodes being in a receptacle having a clear space for light ata place opposite said recess, said receptacle containing inert gas.

2. ln an ionic bombardment light source device of the characterdescribed, the conibination of an electrode comprising a holder tor acathode proper, said holder having a recess therein, a cathode propercomprising a material of substantially high ionemissive properties andhigh heat-resisting properties and being in finelyl divided form tightlypacked in said recess, and an anode electrode in the form of a ringsurrounding the axis of said recess and being, adjacent to said cathodeproper, said electrodes being in a receptacle having a clear space forlight at a place opposite the cathode proper, said receptacle containinginert gas.

3. ln an ionic bombardment light source device of the characterdescribed, the combinaton of an electrode comprising a holder for acathode proper, sai holder havin y a 2P recess therein, a cathode propercomprising a material of substantially high ion-emissive properties andhigh by on deeply heat-resisting roperties and being in finely dividedform tightly packed in said recess, an anode electrode, and a thirdelectrode adjacent to the cathode for starting the operation of thedevice, said electrodes being havin a clear space for light at a placeopposite said recess, said receptacle containing inert gas.

4. In an ionic bombardment light source electrode, and a third in areceptacle device of the character described, the combination of acathode` roper element comprising a material of su stantially highionemissive properties and high heat-resisting properties and being inkti htly compacte form, an anode element, and a starting electrodeelement adjacent to said cathode proper, said elements being in areceptacle having a clear space at a place opposite sai cathode proper,said receptacle containing inert gas.

5. In an ionic bombardment light source device of' the characterdescribed, the coinbination of a cathode electrode having a smallsurface adapted to become incandescent under ionic bombardment, an anodeelectrode adjacent to said cathode and adapted to provide a spark forpreliminarily heating said surface when the device is in normal positionfor use, sai electrodes being within a container having therein an inertgas.

6. In an ionic bombardment light source device of the characterdescribed, the combination of a cathode having a small surface adaptedto become incandescent under ionic ardment, and an anode in the form ofa ring about an axis of said cathode substantially at right angles tosaid surface.

7. In an ionic bombardment light source device of the characterdescribed, a cathode member comprising a metallic holder having highheat-resisting properties and having an open ended recess therein, withannular walls deining said recess at its open end, cathode material insaid recess, sai walls being formed over upon the material and servingas a partial cover and retaining means therefor.

s RAYMOND T. CLOUD.

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